This invention relates to a process for removing iron present as an impurity in molten magnesium. More specifically, the invention relates to a process for reducing the iron contamination in molten magnesium by treating the molten magnesium with a mixture of a boron-containing compound and a flux.
Industrial quantities of magnesium containing low levels of metallic contamination such as iron is highly desirable especially for example, in the pharmaceutical industry where magnesium containing less than about 50 ppm is required for some applications.
Heretofore, BCl.sub.3 has been used to remove metallic impurities such as iron, silicon and manganese from a liquid magnesium by injecting the Bcl.sub.3 in the liquid magnesium. However, this process suffers from the disadvantage that a BCl.sub.3 vapor forms during the process which readily hydrolyzes in air to form HCl acid and an oxide or a hydroxide, therefore, requiring elaborate equipment to contain and carefully meter the reagent to prevent contamination of the foundry atmosphere with acrid smoke. In addition, because of the reactive nature of BCl.sub.3, it must be added slowly to the melt making the overall process slow. Also, BCl.sub.3 is a relatively expensive reagent.
It is desired to provide a novel process, without the problems described above, for effectively reducing metallic impurities such as iron contamination in magnesium. It is further desired to provide a relatively less expensive and simplified process for reducing iron contamination in magnesium using more readily available and easily handled raw materials.